How complete is Blender?
Blender is comprehensive enough to me. On my PC, I have over 25 FREE open alternatives and AFFORDABLES, none of your overpriced. 

Avoid Adobe, if you wish to avoid auto-renewal subscription trap. 

If you want softwares to use alongside Blender, see the list below. 

MyPaint — free lightweight painting software. Great realistic pencils &amp; gritty charcoals there. You will love MyPaint. Great for planning artworks. 

Krita — for digital painting. Has vector and raster formats. Free alternative to Photoshop. 

GIMP — free alternative to Photoshop. 

Note: you can use universal format ORA for working back and forth in all three softwares above. ORA keeps all your layers intact. 

Inkscape — wonderful free alternative to Adobe Illustrator. 

Affinity Designer — affordable alternative to Adobe Illustrator. Has AI format, very useful for opening Illrustrator files or for converting SVG to AI and vice reverse. 

Artrage — affordable software for digital painting. This has highly realistic oil brushes with textured bristle marks on paint. Makes realistic dirt, smudges, smears, etc. 

Rebelle — affordable and unrivalled Software for highly reaslistic watercolour paints that bleed and drip. 

Storyboarder — free open source software for storyboarding.  

Moreover, you can actually upload Photoshop brushes into Krita, Gimp, and Artrage. You can obstain your PS brushes at DeviantArt and Brusheezy. 

Add - I recently created this directory containing thumbnails of scrapbooks, some on open source softwares, if they are of any interest to you. 
https://docs.google.com/presentation/d/1TyUpu4zylhDkEAKpepI9P6HkvtmonJG7zEBLsHgWCjI/